/**
 * 本模块提供贝塞尔曲线工具  
 * 源码来自B站原生header.js工程，具体来源不明  
 * 稍作修改以符合本项目需求
 */
(function () {
    try {
        const NEWTON_ITERATIONS = 4
        const NEWTON_MIN_SLOPE = 0.001
        const SUBDIVISION_PRECISION = 0.0000001
        const SUBDIVISION_MAX_ITERATIONS = 10

        const kSplineTableSize = 11
        const kSampleStepSize = 1.0 / (kSplineTableSize - 1.0)

        const float32ArraySupported = typeof Float32Array === 'function'

        function A(aA1, aA2) { return 1.0 - 3.0 * aA2 + 3.0 * aA1 }
        function B(aA1, aA2) { return 3.0 * aA2 - 6.0 * aA1 }
        function C(aA1) { return 3.0 * aA1 }

        // Returns x(t) given t, x1, and x2, or y(t) given t, y1, and y2.
        function calcBezier(aT, aA1, aA2) { return ((A(aA1, aA2) * aT + B(aA1, aA2)) * aT + C(aA1)) * aT }

        // Returns dx/dt given t, x1, and x2, or dy/dt given t, y1, and y2.
        function getSlope(aT, aA1, aA2) { return 3.0 * A(aA1, aA2) * aT * aT + 2.0 * B(aA1, aA2) * aT + C(aA1) }

        function binarySubdivide(aX, aA, aB, mX1, mX2) {
            let currentX, currentT, i = 0
            do {
                currentT = aA + (aB - aA) / 2.0
                currentX = calcBezier(currentT, mX1, mX2) - aX
                if (currentX > 0.0) {
                    aB = currentT
                } else {
                    aA = currentT
                }
            } while (Math.abs(currentX) > SUBDIVISION_PRECISION && ++i < SUBDIVISION_MAX_ITERATIONS)
            return currentT
        }

        function newtonRaphsonIterate(aX, aGuessT, mX1, mX2) {
            for (let i = 0; i < NEWTON_ITERATIONS; ++i) {
                const currentSlope = getSlope(aGuessT, mX1, mX2)
                if (currentSlope === 0.0) {
                    return aGuessT
                }
                const currentX = calcBezier(aGuessT, mX1, mX2) - aX
                aGuessT -= currentX / currentSlope
            }
            return aGuessT
        }

        function LinearEasing(x) {
            return x
        }

        API.bezier = function (mX1, mY1, mX2, mY2) {
            if (!(0 <= mX1 && mX1 <= 1 && 0 <= mX2 && mX2 <= 1)) {
                throw new Error('bezier x values must be in [0, 1] range')
            }

            if (mX1 === mY1 && mX2 === mY2) {
                return LinearEasing
            }

            // Precompute samples table
            const sampleValues = float32ArraySupported ? new Float32Array(kSplineTableSize) : new Array(kSplineTableSize)
            for (let i = 0; i < kSplineTableSize; ++i) {
                sampleValues[i] = calcBezier(i * kSampleStepSize, mX1, mX2)
            }

            function getTForX(aX) {
                let intervalStart = 0.0
                let currentSample = 1
                const lastSample = kSplineTableSize - 1

                for (; currentSample !== lastSample && sampleValues[currentSample] <= aX; ++currentSample) {
                    intervalStart += kSampleStepSize
                }
                --currentSample

                // Interpolate to provide an initial guess for t
                const dist = (aX - sampleValues[currentSample]) / (sampleValues[currentSample + 1] - sampleValues[currentSample])
                const guessForT = intervalStart + dist * kSampleStepSize

                const initialSlope = getSlope(guessForT, mX1, mX2)
                if (initialSlope >= NEWTON_MIN_SLOPE) {
                    return newtonRaphsonIterate(aX, guessForT, mX1, mX2)
                } else if (initialSlope === 0.0) {
                    return guessForT
                } else {
                    return binarySubdivide(aX, intervalStart, intervalStart + kSampleStepSize, mX1, mX2)
                }
            }

            return function BezierEasing(x) {
                // Because JavaScript number are imprecise, we should guarantee the extremes are right.
                if (x === 0 || x === 1) {
                    return x
                }
                return calcBezier(getTForX(x), mY1, mY2)
            }
        }
    } catch (e) { toast.error("cubicBezier.js", e) }
})();
declare namespace API {
    function bezier(mX1: any, mY1: any, mX2: any, mY2: any): (x: any) => any
}
